Here is the procedure I used to check "pinion slop", sorry, I can't recall the specs, hopefully the Bentley manual lists the limits. Now for the procedure:
1: Jack up the rear end of the car and support it on jack stands.
2: Set the emergency brake to hold the wheels solid or jamb the brake pedal to the floor.
3: Put trans in neutral.
4: Climb underneath the car and manually twist the driveshaft, see / measure how much twist you can get... less is better.

Now for axle bearing end play:

1: Release brakes, remove rear wheels and rotors/calipers.
2: Force the end of the axle up and down while measuring deflection, less is better, once again, numbers elude me as it has been a few years.
3: Finally check in/out play of the axles by pushing / pulling them in/out, measure, compare, less is better.

If either of the above tests result in out of spec readings, they will probably be way out. If so, I would recommend a complete new bone yard rear axle assembly. Make sure you inspect before buying! They should run in the $200 to $300 range.

Finally, before going through all of the above there should be ZERO detectable slop in the U-joints, if there is ANY rotational play in either end, replace the U-joints! Also, if this is a wagon, with the rear hatch closed grab the handle and push/pull on it with the hatch latched. Any clunks indicate it is time for the new spring loaded guides at the base of the hatch.

jorrell
ps. The rear end on our 92 245 with poly bushings is noisy as all heck, it even growls! Yes when I get relocated/moved, a new rear end assembly is in order as well!
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!